Various devices have been used in the past to connect pipes to other structures such as to another pipe or to a pump or valve. With respect to connecting pipes to other structures in general, some devices are known which slidably receive the pipe in a first direction and once the pipe is positioned on the device, the device resists removal of the pipe from the device. Devices referred to generally as external spigots include one or more projections on an outer surface which engage an inner surface of the pipe. An internal or inner spigot device includes one or more projections which face radially inwardly and engage the outer surface of the pipe.
A related device known for connecting pipes to other structures including pipes is a device referred to as a compression fitting. The compression fitting typically includes an outer sleeve member with structure for engaging the outer surface of the pipe. In other words, an inner spigot member is first provided. A separate inner member is then placed within the pipe. The inner member is then expanded to an enlarged position to compress or squeeze the pipe between the inner member and the outer sleeve member. Alternatively, the fitting may include a rigid inner member and a contractible outer member which is contracted to compress or squeeze the pipe onto the inner member. An example of this is a rubber hose clamp.
A known method for joining pipes made from compatible plastics is to melt or fuse the ends of two adjacent lengths of pipe together to join the pipes.
The above-noted pipe junction devices and methods are useable with a variety of different types of pipes. Often the physical properties and characteristics of the pipe impose limitations on using the various pipe junction devices and methods of joining pipe. Pipes made from polyethylene plastic are one type of pipe where problems are encountered because of the properties of the pipe when conventional pipe junction devices and methods are employed. For example, the polyethylene pipe is fairly rigid and is difficult to compress between two members. It will generally only weld to compatible plastics. Other limitations and problems stem from the difficulty in which the devices and methods may be employed. For example, generally the pipes are joined to other pipes or other structures in the field away from the factory during assembly or repair of the pipe system.
Polyethylene pipes are fairly well known in the art and have proven useful in a variety of applications for handling water and other liquids, possibly mixed with solids. Polyethylene pipes are also useful for handling air and other gases. Polyethylene pipes are useful for irrigation, mining, dredging, dewatering, and other uses where gases and liquids, and possibly solids, are transported. Pipes made from polyethylene are useful because they have many desirable properties including being sufficiently rigid and yet flexible and lightweight. Polyethylene pipe is abrasion and corrosion resistant both with respect to the liquids and gases transported through the pipe and with respect to the environment which is exposed to the exterior of the pipe.
While polyethylene pipe has characteristics that make it an excellent choice for piping in many different applications, one continuing problem has been the difficulty in connecting the pipe to another pipe or to structures such as pumps or valves. One known method of connecting two lengths of polyethylene pipe together includes heat fusing or butt fusing the pipes together. Typically, this requires a special machine designed to heat the ends of the pipe and compress them together to form the weld. Quality control and the reliability of the welds when improperly fused may be a problem.
Other known techniques for attaching two lengths of polyethylene pipe together include using internal spigot type structures which are secured around the exterior of the pipes and compress the pipes radially inwardly to maintain the pipes in place with respect to the junction device. For example, a metal sleeve-type device has been employed wherein the sleeve fits over the outside end of the pipe and then is rolled down to mount the sleeve to the pipe. Further structure, such as a plurality of spikes, may be added that penetrate from the sleeve into the pipe to further assist in holding the sleeve on the end of the pipe. These may not provide leak proof joints, are prone to coming loose over time due to the properties of the pipe, and are difficult to install in the field. This type of coupling is comparable to the stub end which requires heat fusing in the field. Another example is structure which comprises at least two separate members which are bolted or otherwise attached around the exterior of the pipe. This too is prone to coming loose over time or may freeze or rust in the attached state.
Other devices for connecting two lengths of polyethylene pipe together include devices which fit inside the end of each pipe and are then provided with a clamp to clamp the pipe to the inner device. These compression-type fittings are prone to failure and are cumbersome to install. Alternatively, a flange joint may be used where one end of the pipe is made to include a special outwardly extending flange attachable to another pipe or other structure having a mating flange.
The known methods of connecting polyethylene pipe to another pipe or to other structure have been plagued by various common problems. One common problem is the reliability of the joint. Another common problem has been that the connecting structure is cumbersome to position and difficult to install in the field. There exists a need for a pipe junction device which permits easy and reliable structure for connecting pipes, such as polyethylene pipes, to another pipe or to other structures.